1. Field of the Invention
This invention relates generally to improvements in sealing boots, and more particularly to a flexible sealing boot used between the cylinder and piston of a hydraulically operated brake system for a vehicle.
2. Description of the Prior Art
A conventional flexible sealing boot and the operation thereof is explained with reference being made to FIG. 5 wherein the numeral 53 designates a flexible sealing boot which is arranged between a piston 52 and a cylinder 51 of a hydraulically operated brake system for a vehicle. The flexible sealing boot 53, which is conventionally made of rubber or a rubber-like material, is formed with inner and outer cylindrical sleeve portions connected to each other by a flexible web portion 53b which is thinner than the inner and outer sleeve portions. The inner sleeve portion 53a is resiliently mounted in an annular groove 52a provided on the peripheral surface of the piston 52 and the outer sleeve portion 53c is resiliently mounted in an annular groove 51a provided on the peripheral surface of the cylinder 51. The resilient mounting is created by the biasing force arising from the difference between the inside diameter of the inner sleeve portion 53a and the outside diameter of the groove 53a of the piston 52 and the biasing force between the inside diameter of the outer sleeve portion 53 c and the outside diameter of the groove 51a of the cylinder 51 in the unstretched condition. However, the thickness of the connecting portion of the web portion 53b and the outer sleeve portion 53c is generally insufficient to prevent damage from foreign objects such for example as road stones. Furthermore, the thickness of the connecting portion of the web portion 53b and the outer sleeve portion 53c is generally insufficient to retain the biasing force of the outer sleeve portion 53c such that the outer sleeve portion 53c is likely to withdraw from the cylinder 51, and the sealing boot 53 can very quickly lose its sealing ability. A split clamping ring 54 has been fitted over the outer sleeve portion 53c in order to prevent withdrawal from the cylinder 51 during operation. However, use of such a split ring 54 tends to pucker the outer sleeve portion 53c in the region of the split ring 54 damaging the outer sleeve portion 53c and resulting in the sealing boot being gripped at discrete points instead of uniformly.